Cover
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
http://mme.modares.ac.ir/article_12798_5bb04cd89d81061990767eda0853cfd1.pdf
IFC
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
0
0
http://mme.modares.ac.ir/article_12799_9ad59bd2bdb47dc1c09375a566e01082.pdf
Content
text
article
2015
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
0
0
http://mme.modares.ac.ir/article_12800_c86df20327e196804b54b6d6b2a869cb.pdf
Dynamic Modeling and Nonlinear Adaptive Control of Mesicopter Flight
Mohammad
Navabi
استادیار مهندسی هوافضا -دانشکده فناوریهای نوین -دانشگاه شهید بهشتی
author
Hamid Reza
Mirzaei
دانشکده مهندسی فناوریهای نوین، دانشگاه شهید بهشتی
author
text
article
2015
per
این مقاله به مدلسازی و کنترل خطی و غیرخطی پرواز مسیکوپتر میپردازد. ابتدا مدل غیرخطی چندورودی-چندخروجی پرنده با در نظر گرفتن دینامیک عملگرها و اثرات ژایروسکوپیک پره و بدنه استخراج شده و سپس از سه روش کنترلی خطی برای رسیدن به پاسخهای سریع با مشخصات عملکردی مناسب استفاده میشود و از نظر تلاش کنترلی تولیدی برای این وسیله پرنده مقایسه میشوند. کنترل بهینه با توجه به ملاحظات مصرف انرژی نسبت به سایر روش های کنترلی مناسب تر می باشد. مسیکوپترها همواره تحت تاثیر عدم قطعیتها قرار میگیرند و روشهای کنترلی کلاسیک برای مقابله با این نامعینیها و پایدارسازی دینامیک ذاتاً ناپایدار پرنده ضعیف میباشند. برای جبران عدم قطعیتهای پارامتری موجود در دینامیک مسیکوپتر از سه روش کنترلی غیرخطی تطبیقی مدل مرجع برای سه حالت متفاوت مبتنی بر معادلات خطی تکورودی-تکخروجی و معادلات خطی چندورودی-چندخروجی و معادلات غیرخطی چندورودی-چندخروجی استفاده میشود. روشهای کنترلی تطبیقی با داشتن مکانیزمهای تخمین سبب ارتقاء عملکرد سیستم در طول پرواز در شرایط مختلف و پایدارسازی وضعیت و کنترل حالتهای سیستم میشوند. پایداری توسط معیار پایدرای لیاپانوف به اثبات رسیده است. نتایج شبیهسازی مبین موفقیتآمیز بودن روش کنترلی تطبیقی برای جبران عدم قطعیتهای پارامتری و همگرایی مجانبی خطای تعقیب میباشد.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
1
12
http://mme.modares.ac.ir/article_12544_3648b6dfa11b92d64c4ee26b49ea0e30.pdf
Three-Dimensional Constrained Optimal Motion Planning for a Six-Degree-of-Freedom Quadrotor Helicopter for Urban Traffic Purposes
Abolfazl
Lavaei Yanesi
Department of New sciences and Technologies, University Of Tehran, Tehran, Iran
author
Mohamad Ali
Amiri Atashgah
استادیار دانشگاه تهران - دانشکده علوم و فنون نوین
author
text
article
2015
per
Traffic issue is an international challenge in the sophisticated countries in which over population is considered as an important factor in creating this problem. Studies show that the accidents’ report during the minimum time is the best way to control the traffics. For this purpose, this paper has been done in such a way that after modeling the flying robot using Newton-Euler equations, a three-dimensional constrained optimal trajectory has been generated through Direct Collocation Approach. In other words, the proposed problem in this paper is first formulated as an optimal control problem. Afterwards, the optimal control problem is discretized through Direct Collocation Technique, which is one of the numerical solving methods of the optimal control problems, and it is transformed into a Nonlinear Programing Problem (NLP). Eventually, the aforementioned nonlinear programming problem is solved via SNOPT which works based on the gradient algorithm like SQP. It should be noted that since the main objective of motion planning in this paper is controlling the urban traffic, the urban constrains are utilized during the trajectory optimization. In other words, all of the high-rise buildings located during the course are modeled by the various cylinders. The efficacy of the aforementioned method is demonstrated by extensive simulations, and in particular it is verified that this method is capable of producing a suitable solution for three-dimensional constrained optimal motion planning for a six-degree-of-freedom quadrotor helicopter for urban traffic purposes.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
13
24
http://mme.modares.ac.ir/article_12547_82f61392ea5b9c37fff3131fa9a5d22e.pdf
Applicatin of deformation and incremental theory of plasticity in the dynamic buckling of rectangular elastoplastic plate
Habib
Ramezannezhad Azarboni
PHD student
author
Mansour
Darvizeh
Professor
author
Abolfazl
Darvizeh
Professor of guilan university
author
Reza
Ansari
Associate Professor of guilan university
author
text
article
2015
per
Nowadays, availability, durability, reliability, weight and strength, as the most important factors in optimum engineering design, are responsible for the widespread application of plates in the industry. Buckling in the elastic or elastoplastic regim is one of the phenomena that can be occurred in the axial compressive loading. Using Galerkin method on the basis of trigonometric shape functions, the elastoplastic dynamic buckling of a thin rectangular plate with different boundary conditions subjected to compression exponetiail pulse functions is investigated in this paper. Based on two theories of plasticity: deformation theory of plasticity (DT) with Hencky constitutive relations and incremental theory of plasticity (IT) with Prandtl-Reuss constitutive relations the equilibrium, stability and dynamic elastoplastic buckling equations are derived. Ramberg-Osgood stress-strain model is used to describe the elastoplastic material property of plate. The effects of symmetrical and asymmetrical boundary conditions, geometrical parameters of plate, force pulse amplitude, and type of plasticity theory on the velocity and deflection histories of plate are investigated. According to the dynamic response of plate the results obtained from DT are lower than those predicted through IT. The resistance against deformation for plate with clamped boundary condition is more than plate with simply supported boundary condition. Consequently, the adjacent points to clamped boundary condition have a lower velocity field than adjacent points to simply supported boundary condition.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
25
33
http://mme.modares.ac.ir/article_12473_425c8b93a66790d2e94f5ddddb246df5.pdf
Energy analysis of using double skin facade with phase change materials in a high-rise building under climatic conditions of Tehran
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Mehran
Saadati Nasab
دانشجوی دانشگاه بیرجند
author
Elahe
Norozi Jajarm
دانشجوی دانشگاه بیرجند
author
text
article
2015
per
Nowadays, using the double skin facades has attracted the attention of many engineers because of its significant effects on the buildings’ energy consumption. The previous researches have shown that the double skin facades have an appropriate thermal performance in the cold season. However, using double skin façade may lead to increase the building’s energy demand in the warm season. Therefore, in the recent years, the idea of using double skin facades with phase change materials (PCM) has been proposed in order to decrease the summer energy consumption of buildings. In this study, a thermal performance analysis has been performed by considering a high-rise building with the phase change material double skin façade in Tehran climatic conditions. The results indicate that although using the ordinary double skin façades can decrease the building’s energy consumption up to 20% in cold months of the year; it can lead to increase the summer cooling load about 4.6%. However, by using double skin façades with the phase change material glazing, the building’s energy consumption in cold and warm seasons may decrease about 40% and 26%, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
34
40
http://mme.modares.ac.ir/article_12474_27509cc0980a8842bded69b7dc99a30f.pdf
Ultrasonic Damage Classification in pipes and plates using Wavelet Transform and SVM
Hamidreza
Ziaiefar
دانشگاه تربیت مدرس
author
Milad
Amiryan
دانشگاه تربیت مدرس
author
Mojtaba
Ghodsi
استادیار دانشگاه تربیت مدرس
author
Farhang
Honarvar
دانشگاه خواجه نصیر
author
Yousef
Hojjat
دانشگاه تربیت مدرس
author
text
article
2014
per
In this paper, we proposed a practical method for classifying damages in pipes and plates using ultrasonic guided waves. The A-scan Pulse-Echo lamb wave ultrasonic tests used in this study. Tests accomplished on isotropic 1050 Aluminum with 0.4 mm thickness. Damages studied here were corrosion and crack which is common in pipe lines and steel structures like vehicles body or aerospace structures. This investigation is done in three steps. First step, experimental testing (making standard sample, lamb wave tests), second step, signal processing (window function, normalizing, wavelet function), third step, using the proper algorithm for classification. In first step, 206 ultrasonic lamb wave tests are measured on standard damaged samples (on pipe and plate) and the signals digitalized. After that, these signal processed and classified by classification algorithm. In this the classification algorithm is the support vector machine (SVM). In machine learning, support vector machines are supervised learning models with associated learning algorithms that analyze data and recognize patterns, used for classification and regression analysis. The results show that the corrosion damage can be distinguished from crack damages with 99% accuracy by proposed algorithm.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2014
41
48
http://mme.modares.ac.ir/article_12545_6f022243870a57cd2d4b768fe6e32d99.pdf
Nonlinear Observer and Controller Design for Low Earth Orbit Satellite Attitude Control System over Network
Ali
Badpa
Tarbiat Modares University
author
Mohammad Taghi
Hamidi Beheshti
Tarbiat Modares University
author
Mahdi
Sojoodi
استادیار عضو هیئت علمی، دانشگاه تربیت مدرس
author
text
article
2015
per
In this paper, an Extended Kalman Filter (EKF) and a model-dependent nonlinear controller over network using the separation principle for Low Earth Orbit (LEO) satellite Attitude Determination and Control Subsystem (ADCS) have been designed. In this context, according to the satellites development trend, ADCS architecture for a broad class of LEO satellites is proposed to stabilize and achieve mission objectives such as precision attitude determination and pointing. This architecture is a Networked Control System (NCS) used to establish connection and communication among control components including sensors, actuators and onboard processors, as well as to share data with other subsystems. Then, by modeling all components of the system, and considering the network effects as a bounded disturbance, the control system is designed to compensate of these effects. For this purpose, estimation and control algorithms including EKF and a model-dependent nonlinear controller is designed such that in addition to achieve desired system performance, the stability of each of them is guaranteed. Afterwards, the nonlinear dynamics model of the satellite in terms of quaternion parameters and angular velocities is presented, and by expression of the separation principle for nonlinear observer and controller design, their convergence and exponential stability conditions based on linearized model of satellite are derived. Proof of theorem shows that the closed-loop system continuously maintained satellite attitude in the specified accuracy range. Finally, simulation results obtained from applying the designed observer and controller on the active satellite in orbit demonstrates the efficiency of the proposed design.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
49
59
http://mme.modares.ac.ir/article_12546_34f0a7070c4c5b2db949c12742ab7d73.pdf
Design and Aerodynamic Analysis of a Morphing Wing with Shape Memory Alloy Actuator
Hamid
Basaeri
Center of Advanced Systems and Technologies (CAST)
School of Mechanical Engineering, College of Engineering, University of Tehran.
author
Mohammad Reza
Zakerzadeh
University of Tehran
author
Aghil
Yousefi Koma
Center of Advanced Systems and Technologies (CAST)
School of Mechanical Engineering, College of Engineering, University of Tehran.
author
Seyed Saeid
Mohtasebi
Center of Advanced Systems and Technologies (CAST)
School of Mechanical Engineering, College of Engineering, University of Tehran.
author
text
article
2015
per
The scope of the current investigation incorporates the entire process involved in design and development of a Shape Memory Alloy (SMA) actuated wing intended to fulfill morphing missions. At the design step, a two Degree-of-Freedom (DOF) mechanism is designed that is appropriate for morphing wing applications. The mechanism is developed in such a way that it can undergo different two DOF, i.e. gull and sweep, so that the wing can have maneuvers that are more efficient. Smart materials commonly are selected as the actuators due to their suitable thermo-mechanical characteristics. Shape Memory Alloy (SMA) actuators are capable of providing more efficient mechanisms in comparison to the conventional actuators due to their large force/stroke generation, smaller size with high capabilities in limited spaces, and lower weight. As SMA wires have nonlinear hysteresis behavior, their modeling should be implemented in a meticulous way. In this work, after proposing a two DOF morphing wing, an aerodynamic analysis of the whole wing for unmorphed and morphed wings is presented. The results show that the performance of the morphed wing in special flight regimes is improved.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
60
70
http://mme.modares.ac.ir/article_12549_28622758ab26b784504f43937f749fff.pdf
New Preliminary Design Method of Pump-Fed System in a Cryogenic LPRE Base on Gradient and Genetic Algorithms
Mohamad Javad
Montazeri
KN. Toosi University of Technology
author
Reza
Ebrahimi
KNToosi University of Technoilogy
author
text
article
2015
per
In this paper, a new method for preliminary design of feed system (FS) in a cryogenic liquid propellant rocket engine (LPRE) has been developed. The cycle type of LPRE is pump-fed system and staged combustion. Engine cycle consists of main turbopump with reactive gas turbine, a fuel booster pump with hydro turbine and an oxidizer booster pump with active gas turbine. This method based on four specifications, proper cavitation number in pumps especially in oxidizer component, power balance between pumps and turbines, strength of material in main rotor of turbopump and mass evaluation of FS determine the type of FS components and calculate initial requirements for preliminary design of each of them. Calculation shows that employing of booster pumps improve the cavitation characteristic of main pumps and consequently decrease FS mass, but causes added mass to fed-system. Optimum point could be achieved through using genetic algorithm, in which all involving parameters could be considered. Results of the method compared with the same engine scheme. Comparison of the results confirms the correctness of the method and enhancement of FS characteristic parameters.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
71
80
http://mme.modares.ac.ir/article_12548_b0e28eb8af2881bf17e0078518de16f2.pdf
Effect of zeta potential on the stabilization of zirconia microparticles suspension using nanoparticle halo mechanism
Hadi
Keramati
دانشگاه صنعتی شریف
author
Mohammad Hassan
Saidi
هیئت علمی دانشگاه صنعتی شریف
author
Mohammad
Zabetian
هیئت علمی دانشگاه تربیت مدرس
author
text
article
2015
per
In many industrial processes, in the middle stages of production, the final product or residuals contains aqueous suspensions. The instability of suspensions is one of the main challenges towards the mentioned processes. Present study is the result of an experimental investigation that analyzed the effect of Silica nanoparticles on the stabilization of Zirconia microsuspension. The effect of Zeta potentialof micro and nanoparticles on theperformance of the stabilization method by generation of nanoparticle halos were studied experimentally. The turbidity of microparticle suspension, was measured before and after addition of nanoparticles at different PH values. The results of experiments shows that for all PH values, the addition of nanoparticles increases the stability of the suspension.The achieved stability is due to the formation of nanoparticle halos that has been observed using a scanning electron microscope (SEM). Nanoparticle halos decreases the Wan der Waals attractive force and increases the electrostatic charge of microparticles and consequently increases the stability of the resultant suspension.The strength of the stability varies with PH values due to the difference in the electric charge. The maximum stability occurs at the isoelectric point of Zirconia microparticles. When microparticles have relatively low electric charge, the potential sink around them are deeper and thus more nanoparticles form halos. The minimum stabilization also occurs when the microparticles have relatively high electric charge that increases the repulsive force between micro and nanoparticles.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
81
88
http://mme.modares.ac.ir/article_12550_6f7ee647fe3e21695475f55e11e33682.pdf
Development of Finite Volume-Lattice Boltzmann Method Based on Circular Function idea in Simulation of Inviscid Compressible Flow in Curvilinear Grid System
Hamed
Jalali
K.N.Toosi University of Technology
author
Masoud
Mirzaei
دانشیار تهران پارس,دانشکده هوافضا دانشگاه خواجه نصیر
author
Saber
Khoei
K.N.Toosi University of Technology
author
text
article
2015
per
Abstract In this research, a finite volume-Lattice Boltzmann Method (FVLBM) for simulation of inviscid compressible flows in 1-D and 2-D structured curvilinear coordinate system is presented. In this simulation, LBM, with new method of Circular Function idea instead of expansion or correction of Maxwelian function was implemented for evaluation of equilibrium distribution functions, moreover, in order to capture discontinuities in the flow field, 3rd order MUSCL scheme was implemented for approximation of convective term. Since in lattice Boltzmann method time step is extremely limited by relaxation time (Knudsen number), we improved performance of FVLBM with a third-order IMEX Rung-Kutta scheme for temporal discretization of BGK-model for archiving greater time step and lower CPU time. Consequently, the present work can be used widely for simulation of actual engineering problems in aerodynamics. Various gas dynamics benchmark problems and applied engineering unsteady problems in curvilinear coordinate grid is solved for validation. The numerical results of the presented method are compared with experimental dates and the results of FVM Euler solutions; there is good agreement between the results of the present method and those of the references.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
89
100
http://mme.modares.ac.ir/article_12551_e2d578feefb8e304244c73cd42afd555.pdf
Free vibration analysis of fractional viscoelastic Euler-Bernoulli nano-beam
Mohammad
Faraji Oskouie
دانشجوی کارشناسی ارشد
author
Reza
Ansari Khalkhali
دانشیار دانشگاه گیلان
author
text
article
2015
per
Fractional calculus is a branch of mathematics which in recent decades has been of great interest to scientists in various disciplines, including engineering. One of the applications of this branch in engineering, is in modeling the viscoelastic materials using fractional differentiation. In this article, by inserting fractional calculus as a viscoelastic material compatibility equations in nonlocal beam theory, a viscoelastic Euler-Bernoulli nano-beam with different boundary conditions at two ends, has been modeled. Material properties of a carbon nanotube is considered and two methods, pure numerical and numerical-analytical have been used for solving obtained equations in time domain. Main method is completely numerical and operator matrices used in it to discrete equations in time and spatial domain. Second method is introduced for validation of pervious method’s answers. In this method equation of system reduced to an ordinary differential equation using Galerkin and obtained equation solved using a numerical direct integrator method. Finally, in a case study, the effects of fractional order, viscoelasticity coefficient and nanlocal theory coefficient on the time response of the viscoelastic Euler-Bernoulli nano-beam with different boundary conditions have been studied.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
101
107
http://mme.modares.ac.ir/article_12552_e35dc345bb13d0597217634d4a37d01c.pdf
Experimental Study on the Water Absorption and Tribological Properties of PA6/CaCO3 Nanocomposites
Ali
Nozad Bonab
دانشجوی کارشناسی ارشد، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات آذربایجان شرقی، گروه مهندسی مکانیک
author
Rasool
Mohsenzadeh
دانش آموخته کارشناسی ارشد در مهندسی مکانیک - ساخت و تولید، دانشکده مهندسی مکانیک، دانشگاه تبریز
author
Mohammad-Reza
Sayyed Noorani
Assistant Professor of Mechatronic Engineering Department, University of Tabriz
author
text
article
2015
per
In this paper, we investigate the effect of nano-CaCO3 on water absorption and tribological properties of polyamide-6. To this end, nanocomposites based on polyamide-6 blend, containing 1 to 5 phr of nano-CaCO3, and 1 phr of maleated polyamide (PA-g-MAH) as compatibilizer, are prepared via melt compounding followed by injection molding. The wear testing of each of the prototypes is carried out under identical conditions. Then, the morphology is studied using scanning electron microscopy. The addition of nano-CaCO3 particles with compatibilizer increases the wear resistance and reduces the water absorption. The results of experiments indicate that minimum wear rate is achieved by adding 1 phr of nano-CaCO3 with compatibilizer which is nearly 4 times less than pure PA6. Furthermore, the presence of nano-CaCO3 together with PA-g-MAH lowers the amount of water absorption as high as 32% wt in compare to pure PA6. In addition to these, this fact is also emerged that effect of compatibilizer is prominent on uniform distribution of the nano-CaCO3 particles among polyamide matrix that it leads to improve the tribological properties of the nanocomposite prototypes in the wear test.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
108
114
http://mme.modares.ac.ir/article_12554_81ed7b41eac7f69ee6578fee24c08a45.pdf
Investigation of Preload Effects on the Linear and Nonlinear Dynamic Analysis of Noncircular Two Lobe Journal Bearing with Micropolar Lubricant
Asghar
Dashti Rahmatabadi
Associate Professor- Yazd University
author
Mahdi
Zaree Mehrjardi
دانشگاه یزد
author
Reza
Rashidi Meybodi
دانشکده مکانیک دانشگاه پیام نور
author
text
article
2015
per
In this work, using finite element method (FEM) the effects of preload factor on the dynamic stability of noncircular two lobe hydrodynamic micropolar lubricated journal bearing based on the linear and nonlinear analytical dynamic models are presented. Assuming that the rotor is solid, the governing Reynolds equations for incompressible lubrication of journal bearing have been modified using micropolar theory. Later, the linear and nonlinear dynamic models, including a certain harmonic disturbances and time dependent trajectory of rotor center are applied to obtain the stability performance of bearing. The 4th order Rung-Kutta method has been used to solve the time dependent equations of rotor motion. Finally, the numerical results for the critical mass parameter and whirl frequency ratio of rotor as the stability characteristics of bearing are evaluated for different values of preload factor and compared together. Results show that the stability performance of two lobe bearing enhances by increasing the amount of bearing noncircularity in terms of the critical mass parameter increase and decrease of the whirl frequency ratio. Also, by comparing two dynamic analysis methods, it is obvious that the results of linear dynamic model are more cautious in different investigated cases. The results of nonlinear dynamic analysis reveal that by increasing the value of preload factor the dynamic response of rotor center involves return to steady state equilibrium position, limit cycle periodic motions and contact between rotor and bearing's shell.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
115
126
http://mme.modares.ac.ir/article_12553_7b6fd60addf3f60cd27a4a60c1a86fc8.pdf
Development of an implicit high order gridless method for inviscid compressible flows
Mahdi
Hashemabadi
PhD Student/Malek Ashtar University of Technology
author
Mostafa
Hadidoolabi
Assistant Professor/Malek Ashtar University of Technology
author
text
article
2015
per
In this paper, an implicit high order discretization has been developed for gridless method. In recent decade, gridless method using a distribution of points has become an important research topic in computational fluid dynamics. Gridless method usually uses the first order Taylor series for discretization of the space derivatives at any points. This paper presents an extension of high order for a central difference gridless method and investigates the results accuracy and performance of this method for solving inviscid compressible flows. Euler equations have been solved in two dimensional using second and fourth order artificial dissipation terms. These terms make a fast gridless method. The method of discretization in time, Explicit and dual-time implicit time discretization are used. In order to reduce the computational cost, local time stepping and residual smoothing techniques are utilized to speed up convergence. The capabilities and accuracy of the method are compared with finite volume method and experimental data for airfoils in transonic and supersonic flows. Results show that the second order accuracy solutions with fewer point distributions indicate higher accuracy when compared to the first order accuracy solutions in transonic and supersonic flows.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
127
136
http://mme.modares.ac.ir/article_12555_3e5b4bf9a862ce046353b641397f5f7d.pdf
Investigation and performance analysis of a hybrid cooling system of air underground channel and direct evaporative cooler
Mehdi
Maerefat
هیئت علمی دانشگاه تربیت مدرس
author
Sadegh
Ahmadi
دانشجوی دکتری تبدیل انرژی/دانشگاه تهران
author
Amin
Haghighi Poshtiri
استادیار تبدیل انرژی/دانشگاه گیلان
author
text
article
2015
per
In the present paper, cooling performance of a hybrid system of air underground channel and direct evaporative cooler to provide cooling load for residential spaces was investigated in summer and its performance evaluation was studied for Tehran,Iran. The study was performed in hottest day of the year in Tehran which has hot and dry condition. At first, mathematical modeling of the hybrid system components was developed then by using the mathematical modeling, outlet air temperature distribution of any component of the proposed hybrid system was calculated. The obtained results imply that air temperature drops about 10°C in underground air channel and 6°C in direct evaporative cooler. andAccording to the obtained temperatures and thermal comfort zone, it was found that the hybrid system is capable in the hottest days of the year to provide thermal comfort for the residental occupants in Tehran. Then, by calculation of the system efficiency, it was found that the efficiency is more than 1 which indicate high performance of the hybrid system. Eventually by comparison between efficiency of the hybrid system and direct evaporative cooler it was found that efficiency of the hybrid system is 45 percent more than direct evaporative cooler. Also the system efficiency is higher than conventional mechanical systems efficiency and it is eco-friendly because of the system is passive. Thus according to present work, the proposed hybrid cooling system could be a suitable alternative for conventional HVAC systems.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
137
144
http://mme.modares.ac.ir/article_12556_0077e3b5c5aedb15166e79814b2a3163.pdf
FSI Simulation of a Small Size Horizontal Axis Wind Turbine to investigate The Effects of Blade Thickness and Material on Blade Deformation
Mohammad Hossein
Giahi
دانشجوی کارشناسی ارشد دانشگاه تربیت مدرس
author
Ali
Jafarian Dehkordi
استادیار دانشگاه تربیت مدرس
author
text
article
2015
per
In the recent years, wind energy had a faster growth compared with the other renewable energies. The interaction between fluid and structure becomes more important as the wind turbine size and its power production capacity increases. In the present research, the effect of wind speed and blade materials on static deformation of a small size horizontal axis wind turbine blade has investigated. The shaft torque and root flap bending moment values obtained from simulation are in a good agreement with experimental data. Results demonstrated that the deformation of the blade increases as the wind speed grows although the increase rate has declined in the mean wind speed range because of the occurrence of separation phenomenon on the blade surface. The effect of blade components materials on blade deformation was investigated and the least deformed configurations were introduced. The thickness of the designated blade components has been investigated by means of the maximum strain theory. The final thickness of the skin, spur and root was estimated by 2.1 mm, 2.8 mm and 10 mm respectively which are 30% less than the primary one.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
145
152
http://mme.modares.ac.ir/article_12557_19a64865786586fe9a41470b2150c7cd.pdf
Failure Prediction of Proximal Femur using quantitative computed tomography based finite element method
Pegah
Amiri Motlagh
Student, Tarbiat Modares University
author
Majid
Mirzaei
دانشیار، دانشگاه تربیت مدرس
author
Vahid
Naeini
Student, Tarbiat Modares University
author
text
article
2015
per
Quantitative computed tomography (QCT) -based finite element analysis is a commonly accepted approach for prediction of mechanical behavior of bones. The objective of this research is to suggest linear criterion in order to accelerate and increase the precision of predicting of failure load in femoral bone. Accordingly, ten fresh frozen femora were QCT scanned and performed to use in this study. The specimens were loaded under eight different orientations. Finite element model for these samples were generated from QCT images, and related mechanical properties were calculated for each single voxel based on the value of density. In addition, the models were analyzed by linear finite element method. Risk factor that defines as the strain energy density divided to yield strain energy for each element was used for calculations of failure load. These values were sorted for particular loads in finite element model, and the correlations between experimental and numerical results were compared. Finally, eight linear criterions for eight different load conditions were presented which shows magnificent correlation between empirical results (average slope: 0.8903 and average R2: 0.8668). These correlations make it possible to accelerate the prediction of femoral fracture load in various orientations. This research shows a robust and fast method for prediction of failure in bones that can be used for multiple loads and orientations.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
153
158
http://mme.modares.ac.ir/article_12558_3c4cc1f2497072004afaf5c991e97cbc.pdf
Tube electromagnetic forming coupled simulation with ANSYS and LS-DYNA and comparison with experimental results
Mojtaba
Kashani
دانشگاه آزاد نجف آباد
author
Ramin
Khamedi
استادیار عضو هیات علمی گروه مکانیک- دانشکده مهندسی- دانشگاه زنجان
author
Hossein
Ebrahimi
شرکت پالس نیرو
author
text
article
2015
per
Electro Magnetic Forming (EMF) is one of the methods for forming the metal plates with high speed; electromagnet force is used as a forming agent in this process. In this thesis, it simulates transient analysis of electromagnetic coil and structure analysis of high speed forming process. Whole of the high speed forming process time is divided in several processes. At the beginning of the first stage the voltage and the geometric, physical and mechanical specifications of the workpiece and coil and the mold are entered to the ANSYS software and the magnetic parameters of the process such as magnetic field density and the simulation current is extracted. Also in this stage magnetic force is obtained in Ansys software and by applying them in workpiece in LS-DYNA software, agent analysis of the process and shape of piece is obtained. In the second stage the pipe deformation obtained in the first stage is transported to the electromagnetic section of process in Ansys software. Also in this process, after forces computation in Ansys, the results sent to the agent section in Ls-Dyna software. This interaction between these two software is repeated several times until whole the process time is finished and final shape of pipe is obtained. The results of simulation are compared whit experimental test results. so The accuracy of this method was confirmed. The simulation and experimental results indicate that with increasing the capacitor energy, the peak current and electromagnet force are increased and finally displacement of pieces also increases.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
159
164
http://mme.modares.ac.ir/article_12559_cad713ecc41962b8c05a24a657bd4a71.pdf
Analytical solution to calculate the stress distribution around a triangular hole in finite isotropic plates under in-plane loading
Mohammad
Jafari
استادیار دانشگاه صنعتی شاهرود
author
Elaheh
Ardalani
دانشجوی کارشناسی ارشد
author
text
article
2015
per
In this paper, stress distribution around a triangular hole in finite isotropic plate under in-plane loading is studied. With the assumption of plane stress conditions, the method employed is based on the analytical solution of Muskhelishvili’s complex variable method and conformal mapping. The finite plate (the ratio of the length of the biggest side of the hole to side of the plate is greater than 0.2) can be considered as isotropic and linearly elastic. For solving the problem, the finite area with a triangular hole in z plan is mapped onto finite area outside a unite circle in ζ plan using the conformal mapping function. The stress function in finite plate with triangular hole is presented by superposition of the stress function for an infinite plate with a triangular hole and ones for a finite plate without a hole. The unknown coefficients in stress function are obtained by using the least square boundary collocation method and applying the appropriate boundary conditions. The effect of hole curvature, hole orientation, plate’s aspect ratio, hole size, type of loading as the effective parameters is investigated. The results based on analytical solution are in a good agreement with the results obtained from the finite element method . The results show that the analysis of the stress distribution in perforated plates that the ratio of the length of the biggest side of the hole to the smallest side of the plate is greater than 0.2, by using the infinite plate theory has a great error.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
165
175
http://mme.modares.ac.ir/article_12560_39ab8314b1d2986f75c80012d0558093.pdf
Molecular Dynamics Simulation of Surface Specifics Effects on the nanoscale fluid flow
Younes
Bakhshan
دانشگاه هرمزگان
author
Alireza
Shadloo Jahromi
دانشجو
author
text
article
2015
per
In the present study, a molecular based scheme has been developed for simulating of surface roughness and cavitation effects on nano- scale flows. In the nano-channel flows, there are some differences on the flow friction between roughness and cavitations which are not well studied. In the presented approach, based on the Molecular Dynamics Simulation (MD), the Lennard-Jones potential is used to modeling the interactions between particles. Each atom of the solid wall is anchored at its lattice site by a harmonic restoring force and its temperature has been controlled by utilizing thermostat.The roughness and cavitation have been implemented on the lower side of channel. To make a comparison between the effect of roughness and cavitation, the same dimension is used for both of them. Obtained results show, those hydrodynamic characteristics of flow and the walls shear stress depends on the roughness and cavitation sizes. The roughness on the bottom wall has more effect than cavity wall on the velocity and density profiles. Also results show that the presence of roughness on the bottom wall respectively increases the shear stress on the bottom wall and decreases its value on the top wall while, the presence of cavitation on the bottom wall has no effect on the top wall and just increase the bottom wall shear stress.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
176
184
http://mme.modares.ac.ir/article_12564_3dce37139fd41832bc0ad011a010d8fe.pdf
Weibull Parameters Transformability of Local Approach to Fracture in Specimens of Different Shapes
Rasoul
Ahmadi
ندارد
author
Ahmad
Mohammadi Najafabadi
ندارد
author
Iraj
Sattarifar
عضو هیئت علمی دانشگاه صنعتی امیرکبیر تهران
author
text
article
2015
per
Failure of mechanical structures may be caused by presence of some defects like cracks. These defects are generally created due to manufacturing processes or in-service applications. Failures due to cleavage fracture usually lead to catastrophic effects, thus studies of such failures are important. Main approaches for fracture assessment of structures are global approach (classical fracture mechanics) and local approach. In the previously presented models of local approach, unknown parameters are introduced which have to be calibrated using experimental fracture data. Despite of existing different calibration methods, obtaining suitable parameters for predicting brittle fracture based on local approach, has been limited in some cases. The purpose of this study is presenting a rational method for predicting brittle fracture in specimens of different shapes to transform it into full scale cases. In this paper, by considering the location parameter of Weibull distribution as a stress triaxiality criteria and modifying the Beremin model, predicting brittle fracture in specimens of different shapes are studied. Also, independence of the parameters from their shapes is shown and eventually a linear relation between location parameter of Weibull distribution and triaxiality factor for the material is presented.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
185
192
http://mme.modares.ac.ir/article_12561_7d444643a12725b91eac2dcb0a25f6c6.pdf
A study of the force and moment resultants around quadrilateral hole in unsymmetric laminates
Mohammad
Jafari
استادیار دانشگاه شاهرود
author
Hasaan Sadat
Ashoori Savadkoohi
دانشجوی ارشد طراحی کاربردی دانشگاه شاهرود
author
text
article
2015
per
In this paper, with the development of the classical Lekhnitskii’s complex variable methods, stress analysis of unsymmetric laminated with a quadrilateral hole has been studied. By using the complex variable method, Lekhnitiskii obtained the stress distribution around a circular and elliptical hole in anisotropic plates. With the extension of this method to unsymmetric composite laminates and by using the conformal mapping, have tried to investigate the stress distribution around non-circular holes. In this article, the effect of various parameters such as aspect ratio of hole shape, hole orientation and bluntness on force and moment resultants around the hole is considered. The results of the effect of these parameters has been presented for [0/90]T and [-45/45]T layup. The finite element method is used to verify the results of the analytical solution. Analytical results are in good agreement with the finite element solution. Based on the analytical results. Unexpectedly circular hole is not the best geometry to reduce the stress concentration in perforated plates and in some cases by selecting the appropriate bluntness for quadrilateral hole, the stress concentration less than circular hole can be achieved. Also, by choosing an appropriate rotation angle and selecting the proper fiber angle for each layer, the stress and moment resultants around the hole can be significantly reduced.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
193
204
http://mme.modares.ac.ir/article_12562_ca4edb558322fd31a8bf8a626acdf889.pdf
Exergy and Exergoeconomic analysis and optimization of cogeneration cycle under solar radiation dynamic model by using Genetic Algorithm
Kaveh
Hanifi Miangafsheh
سایر دانشگاه گیلان
author
Kourosh
Javaherdeh
Guilan University
author
Mortaza
Yari
Tabriz University
author
text
article
2015
per
The performance of a cogeneration cycle with various working fluids is investigated and optimized with an economic approach. Exergy and exergoeconomic models are developed to investigate the thermodynamic performance of the cycle, and to assess the cost of products. In this study, the dynamic model would be registered to search the system behavior during a day. In this study, hydrogen production rate optimal design (HPROD) refrigeration power optimal design (RPOD) and cost optimal design (COD) are considered for analysis and optimization. According to recent parametric studies, boiler, turbine and condensation temperature and turbine inlet pressure affect the unit cost of products significantly. The results show the carbon dioxide and n-octane has a better operation to produce of hydrogen and refrigeration power among other working fluids, respectively. It is observed that, in carbon dioxide cycle, the SUCP is decreased by 8.5% when hydrogen production rate is decreased from 1.811 lit/s to 1.757 lit/s, therefore, in n-octane cycle, SUCP is decreased by 47.4% when refrigeration power is decreased from 9.599 KW to 6.622 KW. The evaluation of exergy destruction demonstrates in which the condenser has the highest exergy destruction, therefore, its rate in COD case is the lowest among the three other states. The results indicate, in carbon dioxide and n-octane cycles, the total exergy destruction and the investment cost rates in the RPOD case is higher than any other cases.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
205
216
http://mme.modares.ac.ir/article_12563_197c7a672f053b626fa2f9f66c3790a6.pdf
Interphase effects on mechanical properties of randomly distributed fiber reinforced composites subjected to off-axis loading
MohammadJavad
Mahmoodi
دانشگاه شهید بهشتی، پردیس فنی مهندسی شهید عباسپور، دانشکده مهندسی مکانیک و انرژی
author
Mohammad Kazem
Hassanzadeh
دانشجوی دکتری، مهندسی مکانیک، دانشگاه گیلان، رشت
author
Reza
Ansari
دانشیار، مهندسی مکانیک، دانشگاه گیلان، رشت
author
text
article
2015
per
Establishing accurate structure–property relationships for three-phase composites is a fundamental task about a reliable design of such materials. In this study, a three-dimensional micromechanics-based analytical model is presented to evaluate the effects of interphase on the mechanical properties of three-phase fibrous composites under off-axis loading. The representative volume element of composites consists of three phases including reinforcement (long fiber), matrix and interphase which all of three phases are assumed to be isotropic and linear elastic. The state of arrangement of fiber within the matrix materials is assumed to be random with uniform distribution and fibers are surrounded by the interphase. The effects of interphase such as its thickness and stiffness on the mechanical properties of fibrous composites under off-axis loading are investigated. Moreover, the influences of fiber volume fraction with and without considering interphase on the response of composite materials are examined. By introducing a parameter which is called the interphase reinforcement ratio, the results demonstrate that the intensity of interphase effects on Young’s modulus of composites increases from 0 degree (longitudinal loading) to 90 degree (transverse loading). The obtained results by the present micromechanical model could be useful to optimal design of composite materials with superior mechanical properties.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
217
226
http://mme.modares.ac.ir/article_12565_0de73deec0181457f24ace12a3cfe578.pdf
CFD study of a variable geometry ejector using R600a to detect optimal geometry for ejector refrigeration system
Amir
Omidvar
دانشجوی دانشگاه فردوسی مشهد- گروه مکانیک دانشکده فنی مهندسی
author
Mohsen
Ghazikhani
دانشیار دانشگاه فردوسی مشهد-گروه مکانیک دانشکده فنی مهندسی
author
Seyed Mohammad Reza
Modarres Razavi
استاد دانشگاه فردوسی مشهد- گروه مکانیک دانشکده فنی مهندسی
author
text
article
2015
per
In this paper, numerical investigation was carried out for the sake of identifying optimum geometry for variable geometry ejector using in solar refrigeration system as the prerequisites to experimental tests. Variable geometry was made by using a movable primary nozzle and movable spindle in it. Vacuum tube collector was postulated as heat source and R600a used as working fluid. Condenser temperature based on Middle East area temperature and evaporator based on operative condition in HVAC system selected. Generator, condenser and evaporator operating temperatures have severe effects on the optimum geometry of ejector. Therefore, for maximum entrain ratio it is necessary to identify optimum geometry to cope with variations in operating condition. The results showed that using a variable geometry ejector is a requirement for cooling during the day. The following fluid structure was compared by entropy generation during mixing and shock phenomena. The results showed there is optimum back pressure to minimize fluid exit entropy. It coincides with critical back pressure. It was found that depending on back pressure maximum entropy generation happen by two reasons, mixing and shock phenomena.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
227
237
http://mme.modares.ac.ir/article_12566_45b3113f88b03d31d65c267f8fee1484.pdf
Resonance Frequency of Acoustic Eccentric Hollow Sphere
yaser
Mirzaei
head of mechanical engineering department
author
Hessam
Mousavi Akbarzadeh
هیات علمی
author
Seyed Mohammad
Hashemi Nejad
هیات علمی
author
text
article
2015
per
An exact three-dimensional elastodynamic analysis for describing the acoustic resonance frequencies of an acoustic eccentric hollow sphere is derived. The Neumann boundary conditions for inner and outer sphere are considered. The translational addition theorem for spherical vector wave functions is employed to enforcing Neumann boundary conditions. The frequency equations in form of exact determinantal equations involving spherical Bessel functions and Wigner 3j symbols are obtained. Due to geometric symmetry for spherical cavity with inner concentric sphere, multiple degenerate acoustic resonance frequencies are occurred. According to the geometry parameters and frequency number, introduction of eccentricity has a different effect on the acoustic resonance frequency shift. Extensive numerical results have been carried out for acoustic resonance frequency of selected inner-outer radii ratios in a wide range of cavity eccentricities. The numerical results describe the imperative influence of cavity eccentricity and radii ratio on the resonance frequency of the acoustic hollow sphere. Some phenomena such as diminishing degenerate resonance frequency, increasing in the number of resonant frequencies through the splitting of degenerate modes and exchanging the mode of resonance frequencies are demonstrated and discussed.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
238
244
http://mme.modares.ac.ir/article_12567_66f12a5660c1ada3828698a5517b23a7.pdf
Static deflection and natural frequency analysis of a two-layered electrostatically actuated microcantilever for finding the optimum configuration
Ehsan
Poloei
دانشگاه خوارزمی
author
Mahdi
Zamanian
دانشگاه خوارزمی
author
Seyed Ali Asghar
Hosseini
دانشگاه خوارزمی
author
text
article
2015
per
In this study, the static deflection and natural frequency of an electrostatically excited patch-coated microcantilever beam are analyzed. The proposed model is considered as the main element of many microsensors and microswitches. Firstly, the nonlinear motion equation is extracted by means of Hamilton principle, assuming shortening effect. Secondly, differential equations, governing the static deflection and free vibration equation around the stability point, are solved using Galerkin method and the three mode shapes of a uniform microbeam are employed as the comparison function. By assuming that the volume of deposited layer is constant, the variation of natural frequency and static deflection are examined in three different cases. In any cases, it is presumed that the second layer is initially deposited on the entire length of microbeam. In the first case, one end of coated layer is considered fix at the clamped side of microcantilever, and then its length is decreased from other side, where its thickness is increased. In the second case, one end of coated layer is perceived fix at the free side of microcantilever, and then its length is decreased from other side, where its thickness is escalated. In the third case, the length of second layer is decreased from both of left and right ends, where its thickness is expanded. In addition, the effect due to the change of the second layer position is considered on mechanical behavior of the system.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
245
253
http://mme.modares.ac.ir/article_12568_acc2c14cc72c19fb25bdb42b34d5c5c8.pdf
Tech economical optimization of CCHP system with rely the time value of money, in payback period
Fateme
Tavakoli Dastjerd
استاد مدعو دانشگاه بزرگمهر قاین
author
Mohammad Mustafa
Ghafuoryan
استاد مدعو دانشگاه بزرگمهر قاینات
author
Seyed Ehsan
Shakib
معاون آموزشی دانشگاه بزرگمهر قاینات
author
text
article
2015
per
In this paper, optimization and techno-economic evaluation of a Combined Cooling, Heating and Power ( CCHP ) system for a hotel in Kerman has been investigated. The design parameters of system includes capacity of gas engine (as prime mover), partial load (PL), thermal capacity of boiler, the cooling capacities of electric and absorption chillers that by using energy, economic, and environment analysis and relative annual benefit (AP), as objective function, have been optimized. Then for optimum results the payback period (PB) has been investigated, by considering the time value of money and without it. Results show increase of number prime mover, reduce the annual benefit and this process has reverse relation with classic payback period since choosing a 2550 kW gas engine, maximum relative annual benefit (AP) with value of 45.5×105 ($/year) and minimum payback period (PB) of 6 years obtains. Also when the costs of energy increases and one prime mover (PM) is selected, the results of traditional and classical payback method are different as the time of payback period increase in classic method and decrease for traditional method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
254
260
http://mme.modares.ac.ir/article_12569_78036774b28c35f2d9d25fa3c50a3674.pdf
Analysis of tensegrity structure subjected to dynamic loading using state space
Shirko
Faroughi
استادیار دانشگاه صنعتی ارومیه
author
Mehdi
Bamdad
عضو هیئت علمی دانشگاه صنعتی شاهرور
author
Seyed Hamed
Hosseini
عضو هیئت علمی دانشگاه
author
text
article
2015
per
Tensegrity is a kind of spatial structural system composed of cable (in tension) and strut (in compression). Stability is provided by the self-stress state between tensioned and compressed elements. When this structure is subjected to external dynamic loading, it may become unstable due to low structural damping. In this study, the proportional damping is considered and dynamical equations of the tensegrity structure are derived based on the equilibrium configuration. In addition the mass of cable element is taken into account. In general, linearized dynamic model provides a good approximation for analyzing the nonlinear behavior of tensegrity structures around an equilibrium configuration. So, state space method is implemented to obtain the dynamic response of the tensegrity system. Two different tensegrity structures are numerically evaluated using this approach in order to show its efficiency. Results reveal how the dynamic analysis of a tensegrity structure is essential. When resonance occurs, the compressive and in-tension members of a tensegrity system may dynamically buckle and slack respectively. In addition, the results show that the computational time to evaluate a tensegrity structure using the state space method is shorter than that of Newmark algorithm.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
261
268
http://mme.modares.ac.ir/article_12570_df42ba87fd3ba6a32fb7d4538f2e8fb6.pdf
Development of a modified friction stir process for dispersion of multi-walled carbon nano-tube throughout nylon 6
Reza
Farshbaf Zinati
Department of Mechanical Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran.
author
text
article
2015
per
In the current work, a modified method of friction stir process (FSP) based on ultrasonic vibration and modified FSP tool design was developed to disperse multi-walled carbon nano-tube (MWCNT) throughout nylon 6 matrix. To this end, Field emission scanning electron microscopy, X-ray diffraction, Vickers’ micro-hardness, and visual inspection were used to evaluate the fabricated nano-composites. Also, a modified design of FSP tool together with ultrasonic vibration were used to improve the impact and efficiency of FSP. Several experiments were conducted to approach an optimum range of FSP parameters (rotational speed and traverse speed). The scanning electron microscopy observations and X-ray diffraction patterns (XRD) declare that MWCNT was dispersed homogeneously throughout nylon 6 matrix. Micro-hardness results illustrate that homogeneous dispersion of MWCNT throughout nylon 6 matrix results in 33% increase of micro-hardness. In general, the obtained results declare that ultrasonic vibration causes an increase in traverse speed and production speed of nano-composite without affecting the homogeneous dispersion and hardness of nano-particles throughout the matrix. Also, it is clear that ultrasonic vibrations did not noticeably affect superficial form of nano-composites due to low traverse speeds used in ultrasonic assisted friction stir process.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
269
278
http://mme.modares.ac.ir/article_12571_964f391a39cd1140fca2c88233994c53.pdf
The effects of compliance mismatch on the End to Side bypass graft
Mehdi
Ramezanpour
دانشجوی کارشناسی ارشد دانشگاه تربیت مدرس
author
Mehdi
Maerefat
عضو هیات علمی دانشکده مکانیک دانشگاه تربیت مدرس
author
Manijhe
Mokhtari-Dizaji
استاد دانشکده علوم پزشکی دانشگاه تربیت مدرس
author
text
article
2015
per
Compliance mismatch is one of the reasons of the coronary artery bypass graft (CABG) failure. The purpose of this study is to investigate the effect of compliance mismatch on the End to Side bypass graft. In order to model non Newtonian behavior of the blood flow, the Carreau–Yasuda model was employed and the graft and artery wall was assumed to be isotropic and modeled as a linearly elastic. In this study also the effects of blood rheology and wall distensibility on the wall shear stress distribution and velocity profile were investigated. The results of the simulation show that the maximum deformation occurs in the critical position of graft-artery junction and compliance mismatch cause smaller wall deformation in comparison to the cases in which the materials of the graft and artery are the same which leads to a higher intramural shear stress in graft-artery junction. The anastomotic wall deforms in a way that always tends to separate the graft and artery. Wall shear stress distribution on the bed centerline and the toe of the bypass graft indicates that the differences between the homologous and non-homologous material case are visible only when the internal pressure is lower than the external one. In the distal location of the artery after the toe of the anastomotic, the values of wall shear stress in the homologous material case are lower than the non-homologous material one.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
279
286
http://mme.modares.ac.ir/article_12572_659631afa7fe5bbcb687d80b0c05dc95.pdf
Uncertainty Quantification of RANS Turbulence Models for Power-law Non-Newtonian Fluid Flows
Vahid
Esfahanian
استاد/مرکز تحقیقات خودرو، سوخت و محیط زیست دانشگاه تهران
author
Iman
Rahbari
دانشجوی کارشناسی ارشد دانشگاه تهران
author
Mohammad Hossein
Mortazavi
دانشجوی کارشناسی ارشد دانشگاه تهران
author
text
article
2015
per
Non-Newtonian fluid flows experience turbulent regime in some industrial applications. Several approaches have been proposed for numerical simulation of turbulent flows that each one has specific features. RANS turbulence models have reasonable computational costs, while include several sources of uncertainties affecting simulation results. In addition, developed RANS models for non-Newtonian fluids are modified versions of available models for Newtonian fluids, therefore, they cannot provide reliable estimation for viscoplastic stress term. On the contrary, DNS delivers accurate results but with high computational costs. Consequently, use of DNS data for estimation of uncertainty in RANS models can provide better decision making for engineers based on RANS results. In the present study, a turbulence model based on for power-law non-Newtonian fluid is developed and employed for simulation of flow in a pipe. Then, an efficient method is proposed for quantification of available model-form uncertainty. Moreover, it is assumed that uncertainties originating from various sources are combined together in calculation of Reynolds stress as well as viscoplastic stress. Deviation of the stresses, computed using RANS turbulence model, from DNS data are modeled through Gaussian Random Field. Thereafter, Karhunen-Loeve expansion is employed for uncertainty propagation in simulation process. Finally, the effects of these uncertainties on RANS results are shown in velocity field demonstrating the fact that the presented approach is accurate enough for statistical modeling of model-form uncertainty in RANS turbulence models.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
287
294
http://mme.modares.ac.ir/article_12573_19d5a05d9aae92e87d06aab967a301e1.pdf
Investigation of effective parameters on darrieus wind turbine efficiency with aerodynamics models
Alireza
ArabGolarche
دانشجوی کارشناسی ارشد، مهندسی مکانیک، دانشگاه فردوسی، مشهد
author
Mohammad
Moghiman
استاد، مهندسی مکانیک، دانشگاه فردوسی، مشهد
author
Seyed Mohammad
Javadi Malabad
دانشگاه مهندسی فناوریهای نوین قوچان
author
text
article
2015
per
Darrieus turbine is a type of vertical axis wind turbines that unlike it's simple structure, behavior analysis is a hard computational task. Because of the complex flows around the machines, aerodynamic optimization problem that still remains an open question. In this paper, a numerical algorithm based on the Double Multiple Stream tube model is used to calculate the effect of the parameters that influence the efficiency of the Darrieus turbine. This method is a semi-empirical method using lift and drag coefficients obtained from experimental data. The comparison between the results of the present study with the experimental measurements shows that although the developed algorithm gives acceptable results, but, for higher rotational speeds gets than nominal rotational velocity, the model accuracy gets lower. The aim of this paper is to find optimal conditions, parametrically analyze the effect of blade thickness, solidity, Reynolds number, pitch angle and aspect ratio on turbine efficiency and start. The results show that increasing thickness, Reynolds number and solidity cause an increase in the turbine self-start capability. On the other hand, increasing the solidity of the turbine will reduce working range, and increasing the aspect ratio will increase efficiency especially at the nominal rotational velocity. The results also show that the designed turbine having variable solidity, can have the benefits of both low and high solidity turbines simultaneously. But manufacturing variable thickness blades doesn't have proper justification. Limited increase in pitch angle can also have positive effect on efficiency.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
295
301
http://mme.modares.ac.ir/article_12575_262ae88408770d72c990de7ea5c94922.pdf
Optimization of dimension and optimal path planning of a Surgical Robot
Anita
Eslami Khotbesara
مدرس دانشگاه
author
Behnam
Miripour Fard
Head of Robotics Eng. Dept
author
text
article
2015
per
The main purpose of this paper is to use the concept of manipulability index for finding the optimal link lengths of a surgical robot and then to plan an optimal path for it. This index depends on the configuration of the robot. In each configuration, the manipulability of the robot is calculated thorough the Forward and Inverse Kinematic and Jacobain. In the present paper, a nonlinear constrained optimization problem is formulated based on this index to find the optimum link lengths. The optimization problem is solved using Genetics Algorithm for entire work space of the robot. The manipulability index is calculated all over the workspace using the Mont-Carlo method. Afterward, using this set of optimal link lengths, the optimal path planning is presented in the Cartesian work space. This optimization is done by considering the manipulability criteria while the tracking error is minimized during performing an operation. The suggested procedure is implemented on a four degree of freedom robot manipulator. Several simulations scenarios are presented to demonstrate the capability of the procedure. The simulation results show the efficiency of the method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
302
308
http://mme.modares.ac.ir/article_12577_b376088f6f0f1755f3f04110ab6fecb9.pdf
Dynamic analysis of the derailment of high-speed railway vehicle on a curved path with longitudinal displacement
Mohamad-Reza
Ghazavi
faculti member TMU
author
Mehrdad
Azari Nejad
دا نشجوی دانشگاه تربیت مدرس
author
Sasan
Rahmanian
دانشجوی کارشناسی ارشد دانشگاه تربیت مدرس
author
text
article
2015
per
In order to avoid unpleasant incidents, it is crucial to maintain the stability for a high-speed railway vehicle. In this research, a high-speed railway vehicle dynamics with 38 degrees of freedom was investigated, adding longitudinal movement equations. Another innovation of this investigation is to determine the critical velocity for the studied railway vehicle and using nonlinear elastic rail for the wheel and rail contact. In this study, the stable and hunting behavior of the system was investigated. To identify the chaotic motion of the system, frequency analysis has been performed. Also, by plotting the Poincaré map, dynamic behavior of the system is illustrated in a discrete state space, which could be a good criteria for the chaotic or periodic behavior of the system. Long-term behavior reveals that at Speeds lower than the critical speed, the system oscillates until it reaches the steady-state of the system. In steady motion, the oscillation continues until the critical speed When the system reaches the critical velocity, the motion on the limit cycle occurs for the first time and when the speed is higher than critical speed, the vibration amplitude increased smoothly. It was observed from the frequency response plot that the hunting frequency evaluated via the linear elastic rail is higher than that of derived using a nonlinear model.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
309
318
http://mme.modares.ac.ir/article_12574_5f64b29e7a76dfb95e8c0770124936ae.pdf
Optimization of point clouds sets registration process using a hybrid algorithm of gravitational search and nelder-mead
Mohammad
Khosravi
Phd Student
author
khalili
khalili
دانشیار هیات علمی- دانشگاه بیرجند
author
Hosseien
Amirabadi
Assistant Professor of Birjand University
author
text
article
2015
per
Optimization has found a widespread application in many branches of science. In recent years, different methods and theories have been developed to find optimal solutions. Optimization algorithms inspired by nature as heuristics solutions to complex problems. Reverse engineering is one of the applications of optimization methods. In reverse engineering a set of scan points are defined relative to a particular coordination. In data registration process the scanned data sets separated and combined to a single coordinate system are called the process of registration. In this research, applications part has been digitized by coordinate measuring machine(CMM) and the process of point clouds registration in experimental on two pieces in position (without translation and with translation case) has been implemented. Using gravitational search algorithm (GSA), particle swarm optimization (PSO) and genetic algorithm (GA) optimization process is optimized and the registration parameters (rotation and displacement) are obtained. The algorithms mentioned, GSA the accuracy displacement, rotational accuracy and better convergence rate and the run time is less. Finally, a hybrid algorithm is proposed which is a combination of GSA, and Nelder-Mead algorithms (GSA-NM). In the proposed algorithm, the initial guess values obtained by GSA and Nelder-Mead algorithm is provided to ensure an accurate response. The proposed hybrid algorithm is superior to GSA and Nelder-Mead, in terms of the number of iterations and the amount of convergence.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
319
328
http://mme.modares.ac.ir/article_12595_a1e0a20c309bddb4ac86be90c8412b74.pdf
Gravity gradient attitude stabilization of a satellite with varying-length boom in circular orbit
Majid
Mohammadi Moghadam
Dept. of Mechanical Engineering,
Tarbiat Modares University,
Tehran, Iran
author
Salman
Farsi
دانشگاه تربیت مدرس
author
text
article
2015
per
In this paper, a method of tri-axial gravity gradient stabilization of satellite in circular orbit is proposed and investigated. In this method, only one actuator is employed. A satellite with varying-length boom is considered consisting of two rigid bodies having the freedom of moving in the boom direction. The only control input is the force between these two bodies to control the varying-length boom. The gravity gradient torque is considered as the only external torque acting on the satellite. The system is under-actuated and has Hamiltonian structure. So, the port-Hamiltonian approach is utilized. The equations of motion of the system are obtained in Hamiltonian formulation. The equilibrium points and their required control inputs are determined. The linearization around the equilibria is carried out and it can be seen that the linear dynamics of pitch-boom and roll-yaw are decoupled. Therefore, the roll-yaw dynamics is linearly uncontrollable. The method of energy shaping and damping injection is used for controller design. The conditions on the energy shaping control law to stabilize the system are determined. Further, the resulting closed-loop system is analyzed. The closed-loop system has center manifolds. Finally, the performance of the closed-loop system, convergence of state trajectory to the center manifold and its non-exponential convergence is shown by simulation.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
329
340
http://mme.modares.ac.ir/article_12596_8e63c5cf81bc5ee073b231499d8f8086.pdf
Experimental study of a non-premixed turbulent flame stabilization with a porous medium
Seyed Abdolmahdi
Hashemi
Kashan Univ.
author
Ehsan
Noori
دانشگاه کاشان
author
Alireza
Aghaei
دانشگاه کاشان
author
text
article
2015
per
In this paper the stabilizing of non- premixed turbulent flame with a porous medium is studied experimentally. One of the approaches taken to stabilize the flame in high thermal capacity is the usage of the porous medium on the burner. A non-premixed burner with natural gas fuel is used. The First, tests are carried out for the conventional burner and then for the combined burner with the carbide ceramics porous medium. In the conventional burner effects of fuel and air velocity and equivalence ratio on flame length, flame lift off and the stability limit are discussed. Porous silicon carbide ceramics with pore densities of 10ppi, 20ppi and 30ppi are used in the combined burner. Experiments are done at 5cm, 10cm and 15cm distances of porous medium from the burner. The viewed flames in the combined burner are grouped into four regimes. In conventional burner flame in a rich mixture is formed and flame length raise with increasing equivalence ratio. The results show that make less in pore density of the medium increases the possibility of flame formation in the porous medium. Moreover it is observed the flame is formed in the porous medium in an average equivalence ratio of φ=0.63, which is almost the equivalence ratio which a immersed flame is formed in a premixed porous burne.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
341
349
http://mme.modares.ac.ir/article_12612_b90d5ab109d68ab88b760fc97794bae5.pdf
Experimental investigation of heat treatment and deformation rate effects on aluminum-steel bonding in cold spin-bonding process
Abolfazl
Masomi
دانشیار پردیس دانشکده های فنی دانشگاه تهران دانشکده مهندسی مکانیک
author
Siavash
Ail Babaei
دانشگاه تهران
author
text
article
2015
per
Cold spin bonding is a new invented method for producing layered composite tubes based on flow-forming process. Bonding strength in this process is dependent to parameters such as initial thickness, rate of deformation, bonding temperature, initial strength, heat treatment temperature, duration of heat treatment and also production parameters like feed rate and spindle RPM. In the present work, effect of rate on thickness reduction, heat treatment temperature and duration of heat treatment on bonding strength of steel and aluminum have been studied. The strength of bonding which produced by cold spin bonding has been measured by peel test and structure investigation has been done by scanning electron microscopy. Among the parameters, heat treatment temperature and after that thickness reduction rate have the most effects on bonding strength and heat treatment duration has less effect in comparison. The results show that the increase of heat treatment temperature up to a certain level increase bonding strength, but above that level the strength will decrease. . This study also has shown that the best condition occur in %50 thickness reduction, heat treatment temperature of 475 degree and 120 minutes of heat treatment in which bonding strength reaches to yield strength of base metal.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
350
356
http://mme.modares.ac.ir/article_12616_0716e2d6eb2cbdae18d0fbdf4669b121.pdf
Experimental investigation and a model presentation for predicting the behavior of metal and alumina powder compaction under impact loading
Hashem
Babaei
استادیار دانشگاه گیلان
author
Tohid
Mirzababaie Mostofi
دانشجوی دکترا دانشگاه گیلان
author
Majid
Alitavoli
دانشیار دانشگاه گیلان
author
Mojtaba
Namdari
دانشجوی کارشناسی ارشد دانشگاه گیلان
author
text
article
2015
per
The purpose of this paper is to investigate those products which are produced by powder compaction procedure under the low rate impact loading by a drop hammer, both theretically and numerically. Experimental section includes checking the efficiency of density, bending strength and elasticity modulus of the product from grain size and different levels of energy. Two kinds of pure aluminum powder in three different size and also their combination with ceramic are used to obtain this. In the numerical section, dimension analysis method is applied in which non-dimensional models for density, bending strength, and elasticity modulus are presented in form of mathematical functions by means of experimental characteristics and data which are categorized to input and output. The purpose of determination of this model is to reach a reliable and satisfactory prediction for final properties of products subjected to impact loading condition. It is worth to note that singular value decomposition approach is used for calculation of linear coefficients vector which has been obtained by non-dimensional parameters.A comparison between these results and experimental data is done by mathematical functions in order to validate the results. The investigation of training and prediction data errors which has been based on root of mean of squares of error and coefficient of determination shows that the obtained results through mathematical functions have acceptable accuracy; hence utilization of the presented mathematical models for predicting the final properties of product subjected to impact loading is desirable.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
357
366
http://mme.modares.ac.ir/article_12613_9255dd2f7a286b77296fee1c9ef3075f.pdf
An inverse method for determination of elastic constants of three-dimensional orthotropic, monoclinic and anisotropic materials
Razieh
Izadi
دانشجوی دکتری
author
Mohammad Rahim
Hematian
استاد دانشکده مهندسی مکانیک دانشگاه شیراز
author
text
article
2015
per
Identification of elastic constants of three-dimensional anisotropic materials is much more complicated than the corresponding one in two-dimensional materials. This is because of the increased number of the elastic constants in three-dimensional materials. In this paper, an inverse method for determination of elastic constants of three-dimensional orthotropic, monoclinic and anisotropic materials using elastostatic measurements is presented. Strain measurements at some sampling points obtained from several elastostatic experiments are considered as the elastic response of the material. The solution is based on minimization of the difference between measured strains and the corresponding calculated ones at sampling points. The finite element method is used for sensitivity analysis, while the Tikhonov regularization method is used for stablizing the solution. Designing a single elastostatic experiment in which all of the material parameters affect the response distinctively is very difficult and seems impossible. By using the data obtained from a few different experiments, we are able to collect enough information to reach a stable and accurate solution. In the present research, 9 constants of orthotropic materials, 13 constants of monoclinic materials and 21 constants of anisotropic materials have been successfully identified. Effects of different parameters on accuracy and efficiency of the proposed method are studied by presenting several numerical examples.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
367
376
http://mme.modares.ac.ir/article_12614_d079f4e50642ff6c6808a1e2976b9b87.pdf
Water/TiO2 nanofluid flow heat transfer and pressure drop through ducts with circular, square and rectangular cross-sections
Amir
Dhshiri Parizi
دانشگاه صنعتی اصفهان
author
Mohammad Reza
Salimpour
دانشیار - دانشگاه صنعتی اصفهان
author
text
article
2015
per
Energy costs have soared rapidly in the last decades. Thus there is a tremendous need for new kinds of working fluids to improve the heating systems performances and to reduce energy consumption. One of the most applicable heating systems are heat exchangers. Study of thermal hydraulic characteristics for laminar fully developed flow through conduits with different cross-sections is significant in the design of heat exchangers. In the present investigation, the thermo-hydraulic behavior of nanofluid trough conduits with circular, square and rectangular cross sectional shapes is studied, experimentally. This investigation aims to study the effect of Reynolds number and shape of cross-section on heat transfer and pressure drop of nanofluid flow. The experiments were conducted for TiO2/water nanofluid with three volume fractions 0, 0.2 and 0.5 under laminar flow regime with constant wall temperature. Analyzed data indicate that friction factors of square and rectangular cases are more than that of circular cross section. Also, it is seen that the addition of nano powder with low volume fraction (0-0.5%) to base fluids does not increase the friction factor remarkably at both circular and non-circular cases. The results show that the Nusselt number of flow through the conduit with circular cross-section is higher than that of non-circular cases. Moreover, it is observed that adding nano powder o base fluid improves heat transfer in sharp corners and therefore its effect is more pronounced in non-circular cross sections.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
377
382
http://mme.modares.ac.ir/article_12615_568c4c5bb028e81ee1340112295714df.pdf
Simulation of Bubble Sonoluminescing Phenomena with Lattice Boltzmann Method
Mohammad Hassan
Rahimyan
دانشیار مهندسی مکانیک دانشگاه تهران
author
Reza
Sadeghi
دانشجوی دانشگاه تهران
author
text
article
2015
per
In the present Paper, solution methods for simulating compressible flows and shock wave simulation by using Lattice Boltzmann Method(LBM) and simulation of shock wave in the bubble with a moving boundary is evaluated. The standard LBM is found to be incapable of predicting compressible flows and confront instabilities in high Mach number flows. But with some efforts that has been made in recent years, new models for stable solutions of the compressible equations are established. Modified Lax–Wendroff finite difference scheme that has stabale solutions has been used for discretizing Lattice Boltzmann equation. In this study models based on the compressible Euler and compressible multispeed Navier-Stokes to simulate compressible lattice Boltzmann method have been used. The dynamics of compressible bubble busing Rayleigh-Plesset equation have been obtained. Simulation of shock wave in the bubble with other computational fluid dynamics methods has been carried out, However, due to the weakness of the Lattice Boltzmann method for compressible flow, no effort to study the physic of this phenomena has been done with this method. The purpose of this simulation is to achieve a distribution of thermodynamic properties through the radius while collapsing and eventually forming the Sonoluminescence phenomena that caused by the collision of shock waves in the center of the bubble to one other,with lattice boltzmann method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
383
391
http://mme.modares.ac.ir/article_12617_0be63b178d025d7e09a1acc0df1658fd.pdf
The Effect of Cutting Parameters and Vibration Amplitude on Cutting Forces in Vibration-Assisted Side Milling Process of Al7022 Aluminum Alloy
Mohammad Mahdi
Abootorabi Zarchi
Assist. Prof., Mech. Eng., Yazd Univ., Yazd, Iran
author
Mohammad Reza
Razfar
عضو هیئت علمی دانشکده مهندسی مکانیک دانشگاه صنعتی امیرکبیر
author
Amir
Abdullah
عضو هیئت علمی دانشکده مهندسی مکانیک دانشگاه صنعتی امیرکبیر
author
text
article
2015
per
Reduction of cutting force in a machining process offers several advantages including increase in tool life, and improvement in the quality of the machined surface. One the new techniques for reducing cutting force relates to ultrasonic vibration assisted machining. In the present paper, one-dimensional ultrasonic vibration-assisted side milling process of Al7022 aluminum alloy has been studied. In order to investigate the effect of cutting speed, feed rate, radial depth of cut, and vibration amplitude on three cutting force components and their resultant, a special experimental setup has been designed and established which applies one dimensional ultrasonic vibration to work piece. Applying the ultrasonic vibrations on milling process, affects mostly on feed component of cutting force which is unidirectional with the work piece vibration, and decreases it by 33.5% in average. Decrease in cutting speed and increase in vibration amplitude, results to increase the separation of tool and work piece from each other in a portion of each vibration cycle, and larger decrease of the feed force. The average decrease of the resultant cutting force in ultrasonic-assisted milling process is 10.8%.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
392
396
http://mme.modares.ac.ir/article_12630_51127f09983c882e13caa384316f40de.pdf
Piecewise Affine Hybrid System Identification Using Adaline Neural Network
Esmaeil
Khanmirza
دانشگاه علم و صنعت ایران
author
Alireza
Mousavi
دانشجو/دانشگاه علم و صنعت ایران
author
Milad
Nazarahari
دانشجو/دانشگاه علم و صنعت ایران
author
text
article
2015
per
Hybrid systems are a group of dynamical system which their behavior described by the interaction of discrete and continuous dynamical system behaviors. One of the subsets of hybrid systems, is piecewise affine system. Piecewise affine system identification, consists of estimating the parameters of each subsystem and the coefficients of the state-input boundary hyperplanes. In order to clustering the state-input space and estimating the feature matrixes simultaneously, bounded error algorithm and adaline neural network are used. It should be said that in this method, there is no need to know the number of linear subsystems of the piecewise affine system. Moreover, it should be noted that the identification method is extended based on on-line data acquisition from system. In continuation, this method is used to identify a benchmark mathematical piecewise affine system. By comparing the results with the reference paper, it is proven that this method has a good performance in clustering the state-input space and estimating the feature matrixes. In the end, by using the proposed method, an active water tank which its equations are described by the form of a piecewise affine system is identified.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
397
404
http://mme.modares.ac.ir/article_12629_ad8314c6e27bfef261da57d8ac63a1f3.pdf
Effect of Soybean Biodiesel on Performance and Emissions of a High-Speed Compression-Ignition Engine
Arman
Hamidi
دانشگاه صنعتی امیرکبیر
author
Seyed Mostafa
Mirsalim
Faculty of Amirkabir University of Technology
author
Barat
Ghobadian
Faculty of Tarbiat Modares University
author
Amirhossein
Parivar
کارشناسی ارشد مهندسی مکانیک دانشگاه صنعتی خواجه نصیر طوسی
author
Saeed
Abdolmaleki
کارشناس ارشد صحه گذاری شرکت تحقیق، طراحی و تولید موتور ایران خودرو
author
text
article
2015
per
Biodiesel is a renewable and sustainable alternative fuel that is derived from vegetable oils and animal fats. In this paper an experimental investigation is conducted to evaluate the use of soybean oil methyl ester (biodiesel) in the diesel fuel at blend ratios of B0, B2, B5 and B10. In this study, the performance and emissions characteristics of conventional diesel fuel and biodiesel fuel blends were compared. The tests were performed at steady-state conditions in a direct injection diesel engine with 90 kW power that was equipped with EGR and with no modification of calibration. The experimental results of brake-specific fuel consumption (BSFC), torque and exhaust temperature as well as carbon dioxide (CO2), smoke, nitrogen oxide (NOx), carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions were presented and discussed. The results of engine performance parameters at different conditions (different load and engine speed) showed that a negligible loss of engine power and a significant increase in brake specific fuel consumption due to lower heating value of biodiesel. Smoke, CO and HC emissions were decreased by increasing blends of soybean oil as compared to pure diesel. However the increase in engine NOx and CO2 emissions were observed with the increase of biodiesel percentage in the blended fuel.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
405
411
http://mme.modares.ac.ir/article_12631_03c6319980c920dd7174d2549f3426a9.pdf
The effect of Basic factors on strain accumulation of pressurized piping elbows under dynamic moments
Seyed Javid
Zakavi
استاد/دانشگاه محقق اردبیلی
author
Mohammad
Nourbakhsh
کارشناسی ارشد
author
text
article
2015
per
Strain accumulation of the components in power-plants and large industries, which causes physical and human costs, has been interested of many researchers in last decades, because of unexpected collapse of these components under periodic loads and internal pressure. In this study, the effect of four basic factors of piping elbow material, frequency of periodic loading (typically below 10 Hz), internal pressure of pipe and periodic dynamic moments on the amount strains accumulation of piping elbows have been considered. Also, the effect of factors variation listed above, on the amount of strains accumulation has been studied. Analyses done in this study, shows that increase in loading frequency, internal pressure and dynamic moments at the end of piping elbow, increases the amount of strains accumulation. Behavior of strain accumulation of two kinds of materials (carbon steel and stainless steel) was investigated in same condition. Studies showed that the strain accumulation in carbon steel are more than stainless steel due to differences in hardness behavior of these materials. The results showed that, stainless steel piping elbow has better performance compared to carbon steel.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
412
418
http://mme.modares.ac.ir/article_12633_7ead8ca5c4bba38e7d77d4b607a5bfad.pdf
Design and construction of thermal conductivity measurement device and measuring of a magnetic nanofluids thermal conductivity
Hadi
Kargar Sharifabad
گروه مهندسی مکانیک، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران
author
Morteza
Mirzaei Amirabad
گروه مهندسی مکانیک، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران
author
text
article
2015
per
Awareness of the thermal conductivity of nanofluids regard to a significant development for use in research,it is necessary with regard to the inability of the analytical and experimental models that presented in most cases, it experimentally thermal conductivity can be measured. In this paper, the design and performance of thermal conductivity of fluids and nanofluidics measurement device without using a Wheatstone bridge is tested. Wheatstone bridge short transient hot wire method has previously been used for construction that requiring complex electronic systems and high power consumption. In this paper, a new method is provided so that no current or voltage is kept constant, but the method of measuring the relative resistance of the copper-clad lacquered with a diameter of 40 microns was used probe is easy to is within reach. The difference between the results of the design references, 1.17% is obtained. In this regard, changes in the magnetic fluid thermal conductivity is studied experimentally. Magnetic fluids are a new class of nanofluids are affected by magnetic fields and their properties can be changed. Fe3O4 magnetic water-based tests for different volume percentages.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
15
v.
5
no.
2015
419
422
http://mme.modares.ac.ir/article_12576_f46b69b012e04f98063166268f372f89.pdf